Circuit breaker with improved current path and contact means

ABSTRACT

A circuit breaker, of the type comprising bridging main contact arms and an arcing contact arm, comprises an improved current path and contact means. The main contact arms and arcing contact arm are supported under the bight portion of an inverted generally U-shaped support member that is pivotally supported, above the bight portion thereof, for movement about a fixed pivot. Contact means on the main contact arms engage slanted stationary contact means generally under the fixed pivot of the support member. Improved means is provided for supporting biasing springs on the contact means.

0 United States Patent 1151 3,662,134 Cellerini 14 1 May 9, 1972 [54] CIRCUIT BREAKER WITH IMPROVED 3,513,275 5/1970 Cellerini et a1. ..200/146 CURRENT PATH AND C NTACT MEANS 0 FOREIGN PATENTS OR APPLICATIONS 826,711 1/1938 France ..200/146 [72] Invent: Albert Beaver 591,594 1/1934 Germany ..200/146 [73] Assignee: Westinghouse Electric Corporation, Pittsburgh, Pa. Primary Examiner-Robert S. Macon Attorney-A. T. Stratton, Clement L. McHale and W. A. [22] Filed: June 11, 1969 Elehik 21 A 1.N 832 099 1 Pp 57 ABSTRACT [52] U.S. C1. 200/146 R A circuit breaker of the type comprising bridging main [51] In. 33/12 tact arms and an arcing contact arm, comprises an improved [58] Field of Search l I 200/146 current path and contact means. The main contact arms and l arcing contact arm are supported under the bight portion of an inverted generally U-shaped support member that is [56] References cued pivotally supported, above the bight portion thereof, for UNITED STATES PATENTS movement about a fixed pivot. Contact means on the main contact arms engage slanted stationary contact means 2,214,471 9/1940 generally under the fixed pivot of the support member. 1ml i proved means is provided for supporting biasing springs on the contact means. 3,215,803 11/1965 3,430,018 2/1969 9 Claims, 6 Drawing Figures PATENTEnm 9 I972 I 3,662,134

' SHEEIEUFZ WITNESSES I 'NVENTOR fa. Albert R. Cellerini BY v mini WV a, fin- ATTORNEY CIRCUIT BREAKER WITH IMPROVED CURRENT PATH I AND CONTACT MEANS CROSS-REFERENCE TO RELATED APPLICATION A circuit breaker similar to the circuit breaker of this invention is disclosed and claimed in the patent to Albert R. Cellerini et al., U.S. Pat. No. 3,5l3,275 issued May 19, 1970 and assigned to the assignee of the instant application.

BACKGROUND AND OBJECTS OF THE INVENTION In the circuit breaker art, it is old to provide a first rigid stationary conductor having a stationary contact thereon, a second rigid stationary conductor spaced from the first stationary conductor and a rigid movable contact arm that cooperates with the stationary contact and that is connected to the second stationary conductor by means of a flexible shunt to thereby provide the complete current path between the first stationary conductor and the second stationary conductor in the closed position of the contacts. The flexible shunt is usually attached to the movable contact arm and to the second stationary conductor by means of rivets or screws, and solder may be provided at the connection. As the circuit breakers are operated over a period of time, these connections can be weakened by the forces acting thereon during'opening and closing operations of the breaker. Moreover, the solder generally has a relatively low melting point so that the connection can further deteriorate under high temperature conditions. Circuit breakers having increased current carrying ratings are more vulnerable to this undesirable weakening and deterioration of the connections. Moreover, as the ratings of the circuit breakers are increased the cross section of the flexible shunt is increased in order to handle the increased current so that for higher rated breakers the shunt can become very bulky necessitating an increase of space in the circuit breaker housing. It is also difficult to provide a shunt that has enough cross section to carry the increased current and that is flexible enough that the shunt will not affect the operation of the movable parts of the breaker by interfering with the mechanical motion and by introducing forces that adversely affect the contact pressure in the closed position of the circuit breaker.

Accordingly, an object of this invention is to provide a circuit breaker with an improved current path structure and contact means that provides a rigid conducting main current path structure between a pair of spaced stationary conductors in the closed position of the contacts.

Another object of this invention is to provide an improved circuit breaker comprising an arc-extinguishing structure and an improved multipole contact structure constructed to open in a sequence that will draw the arcs in proximity to the arcextinguishing structure.

A further object of this invention is to provide an improved insulating-housing type circuit breaker with an improved main current path and contact structure that provides increased reliability in operation over an extended period of time.

Another object of this invention is to provide an improved circuit breaker having an improved contact structure with improved spring support means for biasing a plurality of bridging contacts to provide contact pressure in the closed position of the contacts.

A further object of this invention is to provide an improved circuit breaker having an improved contact structure with improved operating characteristics and with means providing effective contact pressure in the closed position of the contacts.

In the molded-case or insulating housing type circuit breaker art, an overcenter spring means is usually manually operated to operate the contacts between the open and closed positions. As the ratings of the circuit breakers are increased, it is necessary to provide increased contact pressure in order to prevent overheating of the circuit breaker. The means for providing contact pressure should be so constructed and arranged as to provide adequate contact pressure without requiring an overcenter spring means that is so strong that an operator cannot effectively manually operate the breaker.

Thus, another object of this invention is to provide an improved circuit breaker with an improved current path structure and contact means that provides a rigid conducting main current path structure between a pair of spaced stationary conductors in the closed position of the contacts and with improved means providing adequate contact pressure in the closed position of the contacts along with an overcenter spring operating mechanism that can be effectively manually operated.

The invention, both as to structure and operation, together with additional object and advantages thereof, will be best understood from the following detailed description when read in conjunction with the accompanying drawings.

In said drawings:

FIG. 1 is a side sectional view of a circuit breaker constructed in accordance with this invention, with the view disclosing the operating mechanism in the center pole unit of a three-pole circuit breaker;

FIG. 2 is a partial view illustrating the parts in the contactclosed position;

FIG. 3 is a view similar to FIG. 2 illustrating the parts in a position intermediate the open and closed positions;

FIG. 4 is a top plan view of the movable contact structure seen in FIGS. 1-3;

FIG. 5 is a sectional view taken generally along the line V- V of FIG. 4; and

FIG. 6 is a sectional view taken generally along the line VI VI of FIG. 4.

Referring to the drawings, there is shown, in FIG. 1, a molded-case or insulating-housing type circuit breaker 5. The circuit breaker 5 comprises an insulating housing comprising a molded insulating base 11 and molded insulating cover 13. Suitable insulating barrier means separates the housing 11, 13 into three adjacent insulating compartments for housing the the three pole units of the three-pole circuit breaker in a manner well-known in the art. In each pole unit, two terminals 15 and 17 are provided at openings in the base 11 in proximity to the opposite ends of the housing to enable connection of the circuit breaker in an electric circuit. The terminals 15, 17 are of the type specifically described in the patent to A. R. Cellerini, U.S. Pat. No. 3,296,564 issued Jan. 3, 1967.

In each of the three pole-unit compartments of the circuit breaker, there is a rigid stationary conductor 21 and a rigid stationary conductor 23. The conductor 21 is secured to the base 11 of the insulating housing by bolts 25 that are threaded into tapped openings in the conductor 21. The terminal 15 is secured to the flat under surface of the conductor 21 by means of bolts 27 that pass through openings in the arms of the generally T-shaped terminal 15 and that are threaded into tapped openings in the under side of the conductor 21. A stationary contact 29 is fixedly secured to the front of the conductor 21.

A stationary contact 33 is fixedly secured to the front of the conductor 21 adjacent the spacebetween the spaced conductors 21, 23. The rigid conductor 23 is secured to the insulating base 11 by means of a bolt 37 that passes through an opening in a conductor 39 and through an opening in the conductor 23, which bolt 37 is threaded into a tapped insert in an insulating base 11. The conductor 23 comprises a stationary contact surface 43 that will be hereinafter more specifically described. The conductor 39 is a rigid conductor that passes through an opening in a removable trip device 45. The trip device 45 is energized by current in the conductor 39 to effect tripping operations in response to overload currents. The conductor 39 is secured to the conductor 23 and base 11 at one end thereof by means of the mounting bolt 37. The conductor 39 is secured, at the other end, to the base 11 by means of a bolt 49. The terminal 17 is secured to the under surface of the conductor 39 by bolts 27 in the same manner as was hereinbefore described with regard to the terminal 15. The conductors 21, 23, 39 are rigid solid conducting members.

The removable trip device 45 is a thermal-magnetic trip device comprising a latch structure 51 that is automatically released in response to overload currents through any of the pole units of the circuit breaker in order to effect tripping operations of the circuit breaker. The trip device 45 may be of the type more specifically described in the patent to A. R. Cellerini et al., US. Pat. No. 3,141,081.

A single operating mechanism 53, for controlling all three pole units, is mounted in the center pole unit compartment of the circuit breaker. The operating mechanism 53 comprises a supporting frame 55 that comprises spaced supporting plate parts. The supporting frame 55 is secured to the molded insulating base 1 1 by means of bolts 57. The operating mechanism 53 comprises a pivoted inverted generally U-shaped operating lever 59 that is supported for pivotal movement about support pins 61 that are supported on the frame 55. A toggle comprises an upper toggle link 63 and a lower toggle link 65, which links are pivotally connected by means of a knee pivot pin 67. The upper toggle link 63 is pivotally connected to a releasable trip member 69 by means of a pin 71. The trip member 69 is pivotally supported on the frame 55 by means of a pivot pin 72. The lower toggle link 65 is pivotally connected to a contact support member 73, that is part of a movable contact structure 74 of the center pole unit, by means of a pin 75. A pair of over-center tension springs 77 (only one of which is seen in FIG. 1) are supported at one end on the knee pivot 67 and at the other end on the bight portion of the inverted generally U-shaped operating lever 59. The insulating housing 11, 13 is provided with an opening 79 at the front part thereof, and an insulating handle member 81, which is supported on the front of the operating lever 59, protrudes through the opening 79 to permit manual operation of the breaker. The handle 81 comprises an insulating shield part 83 that closes the opening 79 in all positions of the handle 81.

As can be seen in FIGS. 4-6, the bracket 73 is riveted to a contact support member 75. The contact support member 75 is an inverted generally U-shaped rigid metallic support member that is supported for pivotal movement about a pin 87 (FIG. 1) that is supported on the supporting frame 55. A support bracket 88, that is riveted to the support member 75, has an opening therein which receives the pin 87. A rigid insulating tie bar 89 is fixedly secured to the contact support 75 by means of a bracket 90.

The movable contact structure 74 comprises a rigid conducting arcing contact arm 97 and a plurality of rigid conducting bridging contact arms 99, which contact arms are supported on the contact support member 75. A pair of support pins 101 and 102 are mounted on and between the opposite legs of the inverted U-shaped support member 75. The arcingcontact arm 97 is provided with an opening therein for receiving the pin 101 which opening is large enough to permit only pivotal movement of the arcing contact arm 97 on the pin 102. Each of the bridging contact arms 99 is provided with a pair of elongated openings 103 and 104 which receive the pins 101 and 102 respectively for supporting each bridging contact arm 99 on the pins 101, 102. A separate compression spring 105 is captured between a slot 106 in each bridging contact arm 99 and a spring support 107 that is supported on the contact support member 75. As can be seen in FIGS. 4 and 6, each spring 105 extends through a separate opening 108 in the bight portion of the contact support member 75. A separate compression spring 109 is captured between a slot 110 in each bridging contact arm 99 and a spring support 111 that is supported on the member 75. As can be seen in FIGS. 4 and 6, each spring 109 extends through a separate opening 112 in the bight portion of the contact support member 75. A bolt 113 is pivotally connected at the lower end thereof to the arcing contact arm 97 and extends through an opening 115 in an extended portion of the contact support member 75. A unit 116 is threaded on the upper end of the bolt 1 13. A compression spring 117 is supported on the bolt 113 to bias the arcing contact arm 97 downward which movement is limited by the engagement of a tail portion 119 on the arcing contact arm 97 with the bight portion of the contact support member 75. An arcing contact 121 is supported on the arcing contact arm 97. A contact 123 is supported on one end of each bridging contact arm 99, and an arcuate contact surface 125 is provided at the opposite end of each bridging contact arm 99. Each bridging contact arm 99 is a copper member with the arcuate surface on contact 125 being an external copper surface of the arm 99 and with the contact 123 being a contact member that is fixed to the arm 99. The arcing contact 121, which is a contact constructed to withstand the heat of the arc during interruptions, is fixed to the copper arcing contact arm 97. A flexible shunt conductor 131 is connected at one end thereof to the inner end of the arcing contact support arm 97 by means of a screw 133 that passes through a suitable opening in the conductor 131 and that is threaded into a tapped opening in the arm 97. As can be seen in FIG. 1, the flexible conductor 131 is secured to the conductor 23 by means of a screw 137. Solder may also be provided at the connections of the flexible conductor 131.

As can be seen in FIG. 4, the movable contact structure 74 .for the center pole unit comprises a single center arcing contact arm 97 and eight bridging contact arms 99. There are four bridging contact anns 99 on each of the two'opposite sides of the arcing contact 97. Although eight bridging contact arms 99 are disclosed in FIG. 4, it can be understood that this number could be increased or decreased depending on the requirements of the particular breaker.

The contact structures 74 of the two outer pole units are constructed in the same manner as that of the center pole unit (FIGS. 1-6) with suitable support members in the two outer pole units for supporting the pins 87 (FIG. 1) of the movable contact structures 74 of the outer pole units. All of the movable contact structures pivot 74 about the same axis in the breaker with each of the movable contact structures pivoting on a separate pivot pin 87. The three movable contact structures 74 of the three-pole circuit breaker are connected for simultaneous movement by means of the common tie bar 89 which extends across the three-pole unit compartments of the circuit breaker. The tie bar 89 passes through suitable openings in the insulating barriers that separate the pole-unit compartments. When the operating mechanism 53 is operated to drive the center pole unit contact structure 74, all three of the movable contact structures are simultaneously operated by movement of the common tie bar 89 which connects the three contact structures for simultaneous operation.

In each pole unit there is a separate arc-extinguishing structure 147. Each arc-extinguishing structure 147 comprises an insulating casing 149 having a plurality of stack spaced arc plates 151 of magnetic material supported thereon. The are plates 151, in top plan view, are generally U-shaped plates,

supported with the slots or openings aligned such that the associated movable contact arm 97 moves within the aligned openings during opening and closing operations of the breaker. During opening of the contacts the magnetic field around the are between the separating contacts, operating on magnetic plates 151 draws the arc inward to the bight portions of the U-shaped plates where the arc is broken up into a plurality of serially related arc portions and extinguished in the manner well known in the art.

As can be seen in FIGS. 4-6, washers are supported on the pins 101 and 102 to separate the adjacent bridging contact arms 99 from each other and from the legs of the support 75, and to separate the arcing contact arm 97 from the adjacent bridging contact arms 99. An elongated washer 137 (FIG. 4) is positioned on the pin 102 to space the adjacent bridging contact arms 99 in the space that is left in order to accommodate the arcing contact arm 99 at the other end of the movable contact structure 74. As can be seen in FIGS. 46, there are two separate springs 105, 109 biasing each of the bridging contact arms 99 to provide contact pressure. The bight portion of the contact support member 75 is provided with a separate opening therein for each of the springs 105, 109 of each of the bridging contact arms 99. Each of the spring supports 107, 111 is an inverted U-shaped metallic channel member that is welded or otherwise fixedly secured to the bight portion of the contact support member 75. The inverted U-shaped spring supports 107, 111 are unitary channel members that extend across the front of the contact support member 75 and that are welded in position to provide support for the springs 105, 109.

Referring to FIGS. 1-3, it can be understood that the rigid conductor'23 comprises the slanted contact surface 43 that leads at one end to a lower surface 141 and at the upper end to an upper surface 143. The conductor 23 is a copper conducting member with the contact surface 43 being a copper contact surface for cooperating with the arcuate copper contact surfaces 125 of the bridging contact members 29. It is noted that the slanted contact surface 43 is positioned generally below and slightly to the back of the pivot 87 of the movable contact structure 74. As can be understood with reference to FIGS. 1-3, the lowest point of the arcuate contact surface 125 in the open position is lower in the circuit breaker than when in the closed position. The contacts 125 ride up the slanted contact surface 43 during closing operations of the circuit breaker. The position of the contacts 125, 43, relative to the pivot 87, the springs 105 and the pivoted support member 73, is such as to provide good leverage so that increased contact pressure can be provided without requiring unduly strong operating springs 77 that would be difiicult to manually operate. With the contacts 125, 43 being spaced in the open position, there is no resistance to closing of the contacts during the initial movement of the movable contact structure 74 and the surfaces 125, 43 engage during an early part of the closing movement to slowly compress the contact pressure springs 105 as the contacts 125 are forced frontward against the contact 43. The wiping action of the contacts 125, 43 during the closing and openingoperations serves to keep the contacts clean for better conductivity in the closed position of the contacts. As will be hereinafter set forth, the arcs are drawn at the arc-extinguishing end of the movable contact structure.

The operation of the circuit breaker operating mechanism 53 and trip device 45 is more specifically described in the patent to A. R. Cellerini, US. Pat. No. 3,141,081.

The circuit breaker is shown in FIG. 1 in the open position with the releasable trip member 69 in the latched position. In order to close the circuit breaker, the handle structure 81 is moved in a clockwise direction about the pivot 61 from the open or off" position to the closed or on position. During this movement, the springs 77 are moved overcenter to straighten or erect the toggle 63, 65 to thereby pivot the movable contact structure 74 of the center pole unit in a clockwise direction about the pivot 87 to the closed position seen in FIG. 2. With the three movable contact structures 74 being connected for simultaneous movement by means of the tie bar 89, this movement serves to simultaneously move all three of the movable contact structures to the closed position. When it is desired to manually open the circuit breaker, the handle structure 81 is moved in a counterclockwise direction about the pivot 61 to the open or "off" position seen in FIG. 1. This moves the springs 77 overcenter to cause collapse of the toggle 63, 65 to thereby move the movable contact structure 74 of the center pole unit to the open position seen in FIG. 1. This movement, because all of the movable contact structures 74 supported for simultaneous movement by means of the tie bar 89, moves all three of the movable contact structures to the open position. Each of the movable contact structures 74 moves about the associated pivot pin 87 with all of the movable contact structures 74 moving about a common axis.

When the circuit breaker is in the closed position and an overload occurs in any of the three pole-units, the trip device 45 is operated to automatically release the latch structure 51 to thereby release the releasable trip member 69. Upon release of the releasable trip member 69, the springs 77 rotate the trip member 69 in a clockwise (FIG. 1) direction about the pivot 72 to cause collapse of the toggle 63, 65 and movement of the movable contact structures 74 of the three pole-units to the open position. Upon tripping movement of the circuit breaker, the handle structure 81 is moved to an intermediate position in between the off and on" positions to provide a visual indication that the circuit breaker has tripped open.

It is necessary to reset and relatch' the circuit breaker mechanism, following an automatic opening or tripping operation, before the contacts can be closed. Resetting and relatching is achieved by moving the handle structure 81 counterclockwise to the extreme off or open" position. During this movement, a pin member 151, on the operating lever 59, engages a shoulder portion 153 on the releasable trip member 69 to move the trip member 69 in a counterclockwise direction. Near the end of this movement, the free or latch end of the member 69 is reengaged with the latch structure 51 in a well known manner. The circuit breaker then can be manually operated to the closed position by operation of the handle structure 81.

The movement of the movable contact structure 74 during operation of the circuit breaker will be best understood with reference to FIGS. l-3. The contacts are shown in FIG. 2 in the closed position. In this position, the spring 117 biases the arcing contact arm 97 in a clockwise direction to provide contact pressure between the arcing contacts 121, 29. Each pair of springs 105, 109 biases the associated bridging contact arm 99 downward to provide contact pressure between the contacts 123, 33 and between the contacts 125, 43. In the closed position of the contacts, the circuit through each pole unit extends from the terminal 17 through the conductor 39, the conductor 23, the movable contact structure 74, the conductor 21, to the terminal 15. The circuit is bridged from the conductor 23 to the conductor 21 by means of the movable contact structure 74. In the closed position of the contacts, most of the current will pass through the eight solid rigid bridging contact arms 99. Thus, most of the current will extend from the conductor 23 through the contacts 43, 125, the bridging contact arms 99, the contacts 123, 33 to the conductor 21. Some of the current will bridge the conductors 23, 21 through the parallel conducting path from the conductor 23 through the flexible conductor 131, the arcing contact arm 97, the arcing contacts 121, 29 to the conductor 21. With the solid bridging contact arms 99 being provided with relatively low resistance contacts 125, 123 to cooperate with the relatively low resistance contacts 43, 33, and with the contact arms 99 being solid rigid members of good conducting material, most of the current flow in the closed position will flow through the eight bridging contact arms 99 so that the flexible conductor 31, and the connections thereof in the circuit, will carry relatively less current and be less subject to heat rise that could cause deterioration of the connections. Moreover, the flexible conductor 31 can have a lower cross section so that it will take up less space in the circuit breaker housing and so that it will be less likely to cause interference with the mechanical movement of parts and with the contact pressure.

During opening operations of the circuit breaker, the contact support member 75 moves in a counterclockwise direction about the pivot 87. During this movement, the contact arms 97, 99 are first moved from the position seen in FIG. 2 to the position seen in FIG. 3 with the contacts 123, 33 separating before separation of the contacts 121, 29 and before separation of the contacts 125, 43. During this initial movement, the pins 101, 102 move upwardly to the position where the pins 101 draw the bridging contact arms 99 upward separating the contacts 123, 33 while the contacts 125, 43 remain engaged and while the contacts 121, 29 remain engaged. The contacts 121, 29 remain engaged as the contact arm 97 pivots about the pivot 101 until the tail portion 119 engages the bight portion of the contact support member 75 whereupon the arcing contact arm 97 moves as a unit with the contact support member 75. When the contacts 123, 33 separate all the current is momentarily carried through the flexible conductor 31, and arcing contact arm 97. Thereafter the contacts 121, 29 separate and an arc is drawn between these contacts (121, 29) to be extinguished in the arc-extinguishing structure 147 to thereby interrupt the current in the manner hereinbefore described. Near the end of the opening movement, the contacts 125 separate from the stationary contact 43; During the closing operations, the reverse sequence takes place. The contacts 125, 43 first engage, and then the contacts 121, 29 engage and finally the contacts 123, 33 will engage. During the opening operations, the contacts 33, 123

' disengage before the contacts 125, 43 to transfer the current to the arcing contact arm 97 and if there is any arcing between the contacts 33, 123 the arc will occur in proximity to the arcextinguishing structure 147 where the heat can be dissipated into the arc-extinguishing plates 151 and where the arcs, if severe enough, can be magnetically drawn into the plates 151. With the arcing contact arm 97 carrying the full current near the end of the opening operation and separating last to draw the arcs between the contacts 29, 121, the final interrupting arc is extinguished in the arc-extinguishing structure 147.

From the foregoing, it can be understood that there is provided by this invention an improved circuit breaker comprising a pair of spaced solid rigid stationary conductors and a movable contact structure for bridging the spaced conductors in a closed position of the contacts. The spaced conductors are rigid solid members and the movable contact structure comprises a plurality of rigid solid bridging contact arms that bridge the stationary conductors in the closed position to provide a current path of rigid 3 id conductors in the closed position of the contacts. The bridging contact support arms are resiliently mounted on a pair of supporting pins that extend through elongated slots in the bridging contact support arms, which slots are elongated to permit the bridging contact support arms to be spring biased downward for contact pressure in the closed position. A separate pair of springs is provided for biasing each of the bridging contact arms into contactpressure position. The contact support member is provided with a plurality of spaced openings across the bight portion thereof in proximity to each end thereof. A separate inverted generally U-shaped channel spring support member is welded to the contact support member over each of the rows of openings to provide a front spring support for the plurality of springs that extend through the openings and that engage the bridging contact arms to provide the contact pressure. An arcing-contact arm of rigid solid conducting material is pivotally mounted on one supporting pin between two of the bridging contact arms. The arcing contact arm is spring biased about the supporting pin to provide contact pressure in closed position. The arcing contact arm has an arcing contact thereon for cooperating with a stationary arcing contact on one of the rigid stationary conducting members. An arc-extinguishing structure, comprising a plurality of slotted magnetic plates, is positioned in proximity to the stationary arcing contact, and a movable arcing contact arm generally within the slots of the plates to draw an arc that is magnetically drawn back into the plates for extinction in a manner welhknown in the art. A first of the stationary conductors supports the stationary arcing contact in the arc-extinguishing structure, and a first stationary conductor also supports a stationary contact that is positioned in proximity to or adjacent the space between the spaced stationary conductors. The second of the spaced stationary conductors comprises a third stationary contact in proximity to the space between the spaced stationary conductors. A third stationary contact is slanted from a lowerlevel portion of the second spaced stationary conductor to an upper-level portion of the second spaced stationary conductor. The arcing-contact support arm can be termed a first movable and arcing contact, and each of the bridging contact support arms supports a second movable contact for cooperating with the associated second stationary contact the third movable contact cooperating with the associated third stationary contact. Each of the third movable contacts is an arcuate contact surface on the back portion of the associated bridging contact arm for cooperating with the slanted contact or the third stationary contact. The contacts can comprise surfaces of the associated conducting supports or separate contact members welded or otherwise secured to the associated conducting supports. A flexible conductor is connected to the arcing contact support arm and to the second stationary conductor. During opening operations, a second contact opens first so that any are that may be drawn between the bridging contact arms and the associated contacts will be drawn in proximity to the arc-extinguishing structure. When the second contacts open, the arcing contact arm and arcing contacts carry the full current momentarily and as the arcing contacts separate an arc is drawn between the arcing contacts which is extinguished in the arc-extinguishing structure. With the arcuate movable contacts engaging the slanted stationary contacts generally back near the pivot of the movable contact device and under the pivot of the movable contact device, and with the closing and opening force being applied at a position advanced from the pivot of the movable contact device, and with the arcuate contacts constructed so that the arcuate movable contacts are separated from the slanted stationary contacts and engaged the slanted stationary contacts during an early portion of the closing operation so that there is a slow compression of the contact-pressure springs, good contact pressure can be provided without requiring unduly strong closing springs that might interfere with manual operation of the circuit breaker.

The circuit breaker is an insulating-housing for molded base type circuit breaker with a current path extending lengthwise in the breaker housing. With the provision of solid rigid bridging contact support arms bridging the solid rigid stationary conductors 23, 21 there is a current path of solid rigid conductors through the circuit breaker. The parallel current path, that bridges the stationary conductors 23, 21 through the flexible conductor 31 and arcing contact arm 97, conducts only a small part of the current through the associated pole unit in the closed position of the contacts. The parallel current path carries all of the current through the associated pole units for only a short time opening operations of the circuit breaker. The molded-case circuit breaker can effectively carry increased current in a relatively small phase without undue heating and without requiring an unnecessarily large closing spring that would be difficult to manually operate.

While the invention has been disclosed in accordance with the provisions of the patent statutes, it is to be understood that previous changes in the structural details and arrangement of parts thereof may be made without departing from the spirit of the invention.

I claim:

l. A circuit breaker comprising an insulating housing and a circuit-breaker structure supported in said housing,

said circuit-breaker structure comprising a first stationary conductor supported along the back of said housing, a second stationary conductor supported along the back of said housing and being spaced from said first stationary conductor, an arc-extinguishing structure supported at the front of said first stationary conductor, a first and arcing stationary contact means on the front structure, said first stationary conductor in proximity to said arc-extinguishing structure, a second stationary contact means on the front of said first stationary conductor, a third stationary contact means on the front of said second stationary conductor,

a movable contact device, said movable contact device comprising a contact support member, said contact support member being an inverted generally U-shaped member comprising a bight part and a pair of spaced leg parts extending from said bight part generally backward in said housing in a generally parallel relationship, fixed pivot support means in proximity to one end of said support member on the front side of the bight part of said support member supporting said support member for pivotal movement about a fixed pivot between open and closed positions, an arcing contact arm supported on said support member between said spaced leg parts under said bight part, said arcing contact arm being supported on said support member for movement with said support member between open and closed positions and for limited movement relative to said support member, a first and arcing movable contact on said arcing contact arm, a first contact pressure spring means biasing said arcing contact arm relative to said support member toward said first and arcing stationary contact means, a pair of bridging contact arms supported on said support member between said spaced leg parts under said bight part and on opposite sides of said arcing contact arm, said pair of bridging contact arms being supported on said support member for movement with said support member between open and 'closed positions and for limited movement relative to said support member, a second movable contact and a third movable contact on each of said bridging contact arms, a second pressure spring means biasing each of said bridging contact arms relative to said support member toward said second and third stationary contact means, each of said third movable contacts comprising an arcuate contact on the associated bridging contact arm, said third stationary contact means comprising a slanted surface slanted relative to the front-to-back and end-to-end directions of said circuit breaker, said movable contact device being pivotally movable on said fixed pivot support means between closed and open positions to close and open an electric circuit, in the closed position of said contacts said first and arcing movable contact engaging said first and arcing contact means, said second movable contacts engaging said second stationary contact means and said third movable contacts engaging said third stationary contact means,

during each opening operation of said movable contact device said second movable contacts disengaging from said second stationary contact means and thereafter said arcing movable contact disengaging from said first and arcing-stationary contact means and thereafter said third movable contacts disengaging from said third stationary contact means, 7

and during each closing operation of said movable contact device said third movable contacts engaging said third stationary contact means and thereafter said first and arcing movable contact engaging said first and arcing stationary contact means and thereafter said second movable contacts engaging said second stationary contact means.

2. A circuit breaker according to claim 1, said arc-extinguishing structure comprising a plurality of magnetic plates for attracting arcs drawn in proximity thereto to enhance extinction of the arcs, said arcing contact arm comprising a rigid conducting member, a flexible conductor connected to said arcing contact arm and said second stationary conductor to provide a first current path from said second stationary conductor through said flexible conductor said arcing contact arm said first and arcing movable contact said first and arcing stationary contact means to said first stationary conductor in the closed position of said movable contact device,

said circuit-breaker structure comprising a first stationary said first and second stationary conductors comprising rigid conducting members, each of said bridging contact arms comprising a rigid conducting member, each of said bridging contact arms providing a separate second current path from said second stationary conductor through said stationary contact means the associated third movable contact the bridging contact arm the associated second movable contact said second stationary contact means to said first stationary conductor in the closed position of said movable contact device, and during opening operations of said movable contact device said second movable contacts disengaging from said second stationary contact means to transfer the current therethrough to said first current path to thereby provide that said current will be interrupted by extinction of arcs drawn between said first and arcing movable contact and said first and arcing stationary contact means.

3. A circuit breaker according to claim 2, and said third movable contacts engaging said third stationary contact means generally under the fixed pivot of said contact support member.

4. A circuit breaker comprising a circuit-breaker structure,

conductor, a second stationary conductor spaced from said first stationary conductor, an arc-extinguishing structure, a first and arcing stationary contact means on said first stationary conductor in proximity to said arc-extinguishing structure, a second stationary contact means on said first stationary conductor, a third stationary contact means on said second stationary conductor,

a movable contact device, said movable contact device comprising a contact support member supported on a fixed pivot for pivotal movement between open and closed positions, an arcing-contact arm supported on said support member for movement with said support member between open and closed positions and for limited pivotal movement relative to said support member, a first and arcing movable contact on said arcing-contact arm, a first contact-pressure spring means biasing said arcing-contact arm relative to said support member toward said first and arcing-stationary contact means, an elongated bridging contact arm supported on said support member for movement with said support member between open and closed positions and for limited movement relative to said support member, a second movable contact on said bridging contact arm in proximity to one end of said bridging contact arm and a third movable contact on said bridging contact arm in proximity to the other end of said bridging contact arm, a second contact-pressure spring means biasing said bridging contact arm relative to said support member toward said second and third stationary contact means,

said third movable contact being positioned generally under said fixed pivot of said contact support member,

said circuit-breaker structure comprising an over-center spring operating mechanism supported generally above said movable contact device, said over-center spring operating mechanism being operatively connected to said movable contact device intermediate the ends of said movable contact device, said over-center spring operating mechanism being operable between open and closed positions to drive said movable contact device between open and closed positions, in the closed position said first and arcing movable contact engaging said first and arcing stationary contact means said second movable contact engaging said second stationary contact means and said third movable contact engaging said third stationary contact means,

and during each opening operation of said movable contact device said second movable contact disengaging from said second stationary contact means to transfer current to said arcing-contact arm and thereafter said arcing movable contact moving away from said first and arcing stationary contact means whereby an arc is drawn between said first and arcing movable contact and said first and arcing stationary contact means to interrupt the current between said first and second stationary conductors.

5. A circuit breaker according to claim 4, during each opening operation of said movable contact device said second movable contact disengaging from said second stationary contact means and thereafter said arcing movable contact disengaging from said first and arcing-stationary contact means and thereafter said third movable contact disengaging from said third stationary contact means,

and during each closing operation of said movable contact device said third movable contact engaging said third stationary contact means and thereafter said first and arcing movable contact engaging said first and arcing stationary contact means and thereafter said second movable contact engaging said second stationary contact means.

6. A circuit breaker according to claim 4, said second stationary conductor extending lengthwise in said circuit breaker and comprising said third stationary contact means which extends from a lower level in said breaker to an upper level in said breaker, and during closing operations of said circuit breaker said third movable contact moving against said third stationary contact means to move said third movable contact against the bias of said second contact-pressure spring means from a lower level at the instant of contact engagement to an upper level at the completion of said closing operation.

7. A circuit breaker according to claim 5, said contact support member comprising an inverted generally U-shaped support member comprising a bight portion and a pair of oppositely disposed downwardly extending leg portions, a pair of supporting pins extending between said opposite legs of said contact support member, a plurality of said elongated bridging contact arms on each of two opposite sides of said arcing contact arms, each of said bridging contact arms having a first opening therein in proximity to one end thereof for receiving a first of said pins and a second opening therein in proximity to the other end thereof for receiving the second of said pins to supportsaid plurality of bridging contact arms on said pair of supporting pins, and a separate pair of contact-pressure springs for each of said bridging contact arms disposed between the associated bridging contact arm and the bight portion of said contact support member with each of said pairs of springs comprising a first spring biasing a first end of the associated bridging contact arm and a second spring biasing the second end of the associated bridging contact arm to provide contact pressure between the associated bridging contact arm and the associated stationary contact means in the closed position of said movable contact device.

8. A circuit breaker comprising a stationary contact structure, a movable contact structure cooperable with said stationary contact structure, said movable contact structure comprising an inverted generally U-shaped contact support member comprising a bight part and a pair of opposite leg parts, a plurality of bridging contact arms supported on said contact support member under said bight part and between said leg parts, said bridging contact arms being supported on said contact support member for limited movement relative to said contact support member and for movement with said contact support member between open and closed positions, an inverted generally U-shaped spring support member supported on the front of said inverted generally U-shaped contact support member extending across said inverted generally U-shaped contact support member, said generally U-shaped contact support member having spring opening means therein under said generally U-shaped spring support member, and a separate biasing spring for each of said main bridging contact arms captured in said generally U-shaped spring support member and extending through said spring opening means to bias the associated bridging contact arm to provide contact pressure in the closed position of said contacts.

9. A circuit breaker according to claim 8, a pair of said generally U-shaped spring support members supported on the front of said inverted generally U-shaped contact support member extending across said inverted generally U-shaped contact support member in a spaced relationship, said generally U-shaped contact support member having spring opening means therein under each of said generally U-shaped spring support members, a separate pair of said biasing springs for each of said bridging contact arms, each of said separate pair of biasing springs comprising a separate spring captured in each of said generally U-shaped spring support members and extending through the associated spring opening means to bias the associated bridging contact arm to provide contact pressure in the closed position of said contacts. 

1. A circuit breaker comprising an insulating housing and a circuit-breaker structure supported in said housing, said circuit-breaker structure comprising a first stationary conductor supported along the back of said housing, a second stationary conductor supported along the back of said housing and being spaced from said first stationary conductor, an arcextinguishing structure supported at the front of said first stationary conductor, a first and arcing stationary contact means on the front structure, said first stationary conductor in proximity to said arc-extinguishing structure, a second stationary contact means on the front of said first stationary conductor, a third stationary contact means on the front of said second stationary conductor, a movable contact device, said movable contact device comprising a contact support member, said contact support member being an inverted generally U-shaped member comprising a bight part and a pair of spaced leg parts extending from said bight part generally backward in said housing in a generally parallel relationship, fixed pivot support means in proximity to one end of said support member on the front side of the bight part of said support member supporting said support member for pivotal movement about a fixed pivot between open and closed positions, an arcing contact arm supported on said support member between said spaced leg parts under said bight part, said arcing contact arm being supported on said support member for movement with said support member between open and closed positions and for limited movement relative to said support member, a first and arcing movable contact on said arcing contact arm, a first contact pressure spring means biasing said arcing contact arm relative to said support member toward said first and arcing stationary contact means, a pair of bridging contact arms supported on said support member between said spaced leg parts under said bight part and on opposite sides of said arcing contact arm, said pair of bridging contact arms being supported on said support Member for movement with said support member between open and closed positions and for limited movement relative to said support member, a second movable contact and a third movable contact on each of said bridging contact arms, a second pressure spring means biasing each of said bridging contact arms relative to said support member toward said second and third stationary contact means, each of said third movable contacts comprising an arcuate contact on the associated bridging contact arm, said third stationary contact means comprising a slanted surface slanted relative to the front-to-back and end-to-end directions of said circuit breaker, said movable contact device being pivotally movable on said fixed pivot support means between closed and open positions to close and open an electric circuit, in the closed position of said contacts said first and arcing movable contact engaging said first and arcing contact means, said second movable contacts engaging said second stationary contact means and said third movable contacts engaging said third stationary contact means, during each opening operation of said movable contact device said second movable contacts disengaging from said second stationary contact means and thereafter said arcing movable contact disengaging from said first and arcing-stationary contact means and thereafter said third movable contacts disengaging from said third stationary contact means, and during each closing operation of said movable contact device said third movable contacts engaging said third stationary contact means and thereafter said first and arcing movable contact engaging said first and arcing stationary contact means and thereafter said second movable contacts engaging said second stationary contact means.
 2. A circuit breaker according to claim 1, said arc-extinguishing structure comprising a plurality of magnetic plates for attracting arcs drawn in proximity thereto to enhance extinction of the arcs, said arcing contact arm comprising a rigid conducting member, a flexible conductor connected to said arcing contact arm and said second stationary conductor to provide a first current path from said second stationary conductor through said flexible conductor said arcing contact arm said first and arcing movable contact said first and arcing stationary contact means to said first stationary conductor in the closed position of said movable contact device, said first and second stationary conductors comprising rigid conducting members, each of said bridging contact arms comprising a rigid conducting member, each of said bridging contact arms providing a separate second current path from said second stationary conductor through said stationary contact means the associated third movable contact the bridging contact arm the associated second movable contact said second stationary contact means to said first stationary conductor in the closed position of said movable contact device, and during opening operations of said movable contact device said second movable contacts disengaging from said second stationary contact means to transfer the current therethrough to said first current path to thereby provide that said current will be interrupted by extinction of arcs drawn between said first and arcing movable contact and said first and arcing stationary contact means.
 3. A circuit breaker according to claim 2, and said third movable contacts engaging said third stationary contact means generally under the fixed pivot of said contact support member.
 4. A circuit breaker comprising a circuit-breaker structure, said circuit-breaker structure comprising a first stationary conductor, a second stationary conductor spaced from said first stationary conductor, an arc-extinguishing structure, a first and arcing stationary contact means on said first stationary conductor in proximity to said arc-extinguishing structure, a second stationary contact means on said first stationary conductor, a third stationary contact means On said second stationary conductor, a movable contact device, said movable contact device comprising a contact support member supported on a fixed pivot for pivotal movement between open and closed positions, an arcing-contact arm supported on said support member for movement with said support member between open and closed positions and for limited pivotal movement relative to said support member, a first and arcing movable contact on said arcing-contact arm, a first contact-pressure spring means biasing said arcing-contact arm relative to said support member toward said first and arcing-stationary contact means, an elongated bridging contact arm supported on said support member for movement with said support member between open and closed positions and for limited movement relative to said support member, a second movable contact on said bridging contact arm in proximity to one end of said bridging contact arm and a third movable contact on said bridging contact arm in proximity to the other end of said bridging contact arm, a second contact-pressure spring means biasing said bridging contact arm relative to said support member toward said second and third stationary contact means, said third movable contact being positioned generally under said fixed pivot of said contact support member, said circuit-breaker structure comprising an over-center spring operating mechanism supported generally above said movable contact device, said over-center spring operating mechanism being operatively connected to said movable contact device intermediate the ends of said movable contact device, said over-center spring operating mechanism being operable between open and closed positions to drive said movable contact device between open and closed positions, in the closed position said first and arcing movable contact engaging said first and arcing stationary contact means said second movable contact engaging said second stationary contact means and said third movable contact engaging said third stationary contact means, and during each opening operation of said movable contact device said second movable contact disengaging from said second stationary contact means to transfer current to said arcing-contact arm and thereafter said arcing movable contact moving away from said first and arcing stationary contact means whereby an arc is drawn between said first and arcing movable contact and said first and arcing stationary contact means to interrupt the current between said first and second stationary conductors.
 5. A circuit breaker according to claim 4, during each opening operation of said movable contact device said second movable contact disengaging from said second stationary contact means and thereafter said arcing movable contact disengaging from said first and arcing-stationary contact means and thereafter said third movable contact disengaging from said third stationary contact means, and during each closing operation of said movable contact device said third movable contact engaging said third stationary contact means and thereafter said first and arcing movable contact engaging said first and arcing stationary contact means and thereafter said second movable contact engaging said second stationary contact means.
 6. A circuit breaker according to claim 4, said second stationary conductor extending lengthwise in said circuit breaker and comprising said third stationary contact means which extends from a lower level in said breaker to an upper level in said breaker, and during closing operations of said circuit breaker said third movable contact moving against said third stationary contact means to move said third movable contact against the bias of said second contact-pressure spring means from a lower level at the instant of contact engagement to an upper level at the completion of said closing operation.
 7. A circuit breaker according to claim 5, said contact support member comprising an inverted generally U-shaped support member comprising a bight poRtion and a pair of oppositely disposed downwardly extending leg portions, a pair of supporting pins extending between said opposite legs of said contact support member, a plurality of said elongated bridging contact arms on each of two opposite sides of said arcing contact arms, each of said bridging contact arms having a first opening therein in proximity to one end thereof for receiving a first of said pins and a second opening therein in proximity to the other end thereof for receiving the second of said pins to support said plurality of bridging contact arms on said pair of supporting pins, and a separate pair of contact-pressure springs for each of said bridging contact arms disposed between the associated bridging contact arm and the bight portion of said contact support member with each of said pairs of springs comprising a first spring biasing a first end of the associated bridging contact arm and a second spring biasing the second end of the associated bridging contact arm to provide contact pressure between the associated bridging contact arm and the associated stationary contact means in the closed position of said movable contact device.
 8. A circuit breaker comprising a stationary contact structure, a movable contact structure cooperable with said stationary contact structure, said movable contact structure comprising an inverted generally U-shaped contact support member comprising a bight part and a pair of opposite leg parts, a plurality of bridging contact arms supported on said contact support member under said bight part and between said leg parts, said bridging contact arms being supported on said contact support member for limited movement relative to said contact support member and for movement with said contact support member between open and closed positions, an inverted generally U-shaped spring support member supported on the front of said inverted generally U-shaped contact support member extending across said inverted generally U-shaped contact support member, said generally U-shaped contact support member having spring opening means therein under said generally U-shaped spring support member, and a separate biasing spring for each of said main bridging contact arms captured in said generally U-shaped spring support member and extending through said spring opening means to bias the associated bridging contact arm to provide contact pressure in the closed position of said contacts.
 9. A circuit breaker according to claim 8, a pair of said generally U-shaped spring support members supported on the front of said inverted generally U-shaped contact support member extending across said inverted generally U-shaped contact support member in a spaced relationship, said generally U-shaped contact support member having spring opening means therein under each of said generally U-shaped spring support members, a separate pair of said biasing springs for each of said bridging contact arms, each of said separate pair of biasing springs comprising a separate spring captured in each of said generally U-shaped spring support members and extending through the associated spring opening means to bias the associated bridging contact arm to provide contact pressure in the closed position of said contacts. 